1. FIELD
The subject invention is in the field of constant force springs and spring systems, otherwise known as flat rate springs and spring systems. In particular, it is in the field of such springs and spring systems used in applications in which the deflections of the spring or spring system occur slowly, such as in film and tape cartridges.
2. PRIOR ART
There is much prior art in this general field. There is relatively limited prior art in the particular field in which there are size, shape and space constraints. Examples of the particular prior art are shown in the following U.S. Patents, all issued to the inventor of the subject invention.
______________________________________ 4,986,678 4,990,008 4,998,833 ______________________________________
The spring systems disclosed in these patents require adjustments during use in tape and film cartridges in order to keep the spring forces constant within desired limits as the tape or film is transferred from spool to spool. Accordingly, the primary objective of the subject invention is to provide a spring system which has an essentially flat rate over its entire working deflection. A second objective is that the subject system be adaptable to use in the confined and limited space in film and tape cartridge.